Glossary of Terms

chemosensory organs located between the head and the trunk at both sides of the body

Blastema

a group of proliferating and differentiating cells that coalesce at a wound to give rise to a new body part

Ectoderm

the outermost of the three primary germ layers of an embryo, that forms epidermis and nervous system

Endoderm

the innermost of the three primary germ layers of an embryo, that forms the gut and associated structures

Mesoderm

the middle of the three primary germ layers of an embryo, that forms several structures, such as the connective tissue and the excretory system

Polarity

the asymmetric distribution of specific features in a cell, tissue or organism that determines axial and/or spatial orientation

Protonephridia

The excretory system of the worms. Like the kidney, it is a system of branching tubules that maintain the osmoregulatory balance of the body. Each protonephridia is a single unit of the system and it is constituted of a bundle flame cells, attached to tube cells that open externally through pores.

Remodeling

the reorganization of cells and tissues contained in a regenerating fragment that ultimately re-establishes proper body proportions in the new animal

Riboprobe

fragment of RNA synthesized in vitro whose nucleotide sequence is complementary to the target endogenous mRNA. The nucleotides of the riboprobe are labeled with small molecules (e.g., digoxigenin, dinitrophenol or fluorescein) such that the riboprobe can be detected and localized to cells and tissues under the microscope.

RNAi

a technique that uses double-stranded RNA molecules to inhibit the expression of a specific gene to examine the effect of its absence

Stem cell

an undifferentiated cell that is capable of dividing and giving rise to more stem cells and to differentiated tissue-specific cells

Totipotent cell

a cell with the potential to give rise to all the cell types of the body and extra-embryonic tissues

Transcriptome

the sum of all RNA molecules expressed in a cell, tissue, organ or organism in a specific moment and condition